libbpf: bpf_test_run_opts has non-zero extra bytes

[liangcheng-yu]

Hi, I happened to setup uBPF on two different VMs, both with a clean Ubuntu 20.04.06 LTS and the same clang version etc.
For VM1 it gave me 100% tests passed, while VM2 8 tests failed (iovisor/ubpf#266 (comment)).
Below are the details:

# The one with 100% tests passed
lc@vm1:~/ubpf$ sudo build/bin/bpf_conformance_runner --test_file_path tests/add.data --plugin_path build/external/bpf_conformance/bin/libbpf_plugin  --debug true
Test file: "tests/add.data"
Input memory:
Expected return value: 3
Expected error string:
Byte code: b4  00  00  00  00  00  00  00  b4  01  00  00  02  00  00  00  04  00  00  00  01  00  00  00  0c  10  00  00  00  00  00  00  95  00  00  00  00  00  00  00
Test "tests/add.data" succeeded
Test results:
PASS: "tests/add.data"
Passed 1 out of 1 tests.

lc@vm1:~/ubpf$ echo b4  00  00  00  00  00  00  00  b4  01  00  00  02  00  00  00  04  00  00  00  01  00  00  00  0c  10  00  00  00  00  00  00  95  00  00  00  00  00  00  00 | sudo build/external/bpf_conformance/bin/libbpf_plugin
3

lc@vm1:~/ubpf$ echo b4  00  00  00  00  00  00  00  b4  01  00  00  02  00  00  00  04  00  00  00  01  00  00  00  0c  10  00  00  00  00  00  00  95  00  00  00  00  00  00  00 | sudo strace build/external/bpf_conformance/bin/libbpf_plugin
.... [removed for readability]
bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_XDP, insn_cnt=5, insns=0x7bff30, license="MIT", log_level=0, log_size=0, log_buf=NULL, kern_version=KERNEL_VERSION(0, 0, 0), prog_flags=0, prog_name="", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS, prog_btf_fd=0, func_info_rec_size=0, func_info=NULL, func_info_cnt=0, line_info_rec_size=0, line_info=NULL, line_info_cnt=0, attach_btf_id=0, attach_prog_fd=0}, 128) = 3
bpf(BPF_PROG_TEST_RUN, {test={prog_fd=3, retval=0, data_size_in=0, data_size_out=0, data_in=NULL, data_out=NULL, repeat=1, duration=0, ctx_size_in=0, ctx_size_out=0, ctx_in=NULL, ctx_out=NULL}}, 128) = 0
fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(0x88, 0x1), ...}) = 0
write(1, "3\n", 23
)                      = 2
exit_group(0)                           = ?
+++ exited with 0 +++

# The VM with 8 failed tests
lc@vm2:~/ubpf$ echo b4  00  00  00  00  00  00  00  b4  01  00  00  02  00  00  00  04  00  00  00  01  00  00  00  0c  10  00  00  00  00  00  00  95  00  00  00  00  00  00  00 | sudo build/external/bpf_conformance/bin/libbpf_plugin
libbpf: bpf_test_run_opts has non-zero extra bytes

lc@vm2:~/ubpf$ sudo build/bin/bpf_conformance_runner --test_file_path tests/add.data --plugin_path build/external/bpf_conformance/bin/libbpf_plugin  --debug true
Test file: "tests/add.data"
Input memory:
Expected return value: 3
Expected error string:
Byte code: b4  00  00  00  00  00  00  00  b4  01  00  00  02  00  00  00  04  00  00  00  01  00  00  00  0c  10  00  00  00  00  00  00  95  00  00  00  00  00  00  00
Test results:
ERROR: "tests/add.data" Plugin returned invalid return value
Passed 0 out of 1 tests.

lc@vm2:~/ubpf$ echo b4  00  00  00  00  00  00  00  b4  01  00  00  02  00  00  00  04  00  00  00  01  00  00  00  0c  10  00  00  00  00  00  00  95  00  00  00  00  00  00  00 | sudo strace build/external/bpf_conformance/bin/libbpf_plugin
execve("build/external/bpf_conformance/bin/libbpf_plugin", ["build/external/bpf_conformance/b"...], 0x7ffe1108d920 /* 15 vars */) = 0
.... [removed for readability]
bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_XDP, insn_cnt=5, insns=0x2181f30, license="MIT", log_level=0, log_size=0, log_buf=NULL, kern_version=KERNEL_VERSION(0, 0, 0), prog_flags=0, prog_name="", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS, prog_btf_fd=0, func_info_rec_size=0, func_info=NULL, func_info_cnt=0, line_info_rec_size=0, line_info=NULL, line_info_cnt=0, attach_btf_id=0, attach_prog_fd=0}, 128) = 3
write(2, "libbpf: bpf_test_run_opts has no"..., 51libbpf: bpf_test_run_opts has non-zero extra bytes
) = 51
exit_group(0)                           = ?
+++ exited with 0 +++

For context, both VMs have the same clang, OS version, and apt show libbpf-dev prints, and I set up the environment with the same exact set up scripts and cmake build/test instructions

Package: libbpf-dev
Version: 1:0.5.0-1~ubuntu20.04.1
Priority: optional
Section: universe/libdevel
Source: libbpf (0.5.0-1~ubuntu20.04.1)
Origin: Ubuntu
Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>
Original-Maintainer: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 802 kB
Depends: libbpf0 (= 1:0.5.0-1~ubuntu20.04.1), libelf-dev, zlib1g-dev
Download-Size: 188 kB
APT-Manual-Installed: yes
APT-Sources: http://us-east-1.ec2.archive.ubuntu.com/ubuntu focal-updates/universe amd64 Packages
Description: eBPF helper library (development files)
libbpf is a library for loading eBPF programs and reading and
manipulating eBPF objects from user-space.
.
This package is needed to compile programs against libbpf.